Integrating hydraulic brake booster

ABSTRACT

A power booster for a brake system in which input force and input displacement hysteresis relative to output pressure is avoided or minimized.

1.111111% Memes W1111e1111 1151 3,M 3,4316

11111611 1111 1 Feb. 22, 119721 154] mmonmmme m limmumfi ERAKQE 2,164,760 7/1959 Wesson ..251/44 momma 3,148,592 9/1964 Schultz et a1. ..60/54.6 1 3,298,177 1 1967 11 11 .611 54.5 P

[721 Invenw Mich- 5 327,479 6/1967 11213:; et a1. ..60/54.6 P

[73] Assignee: Kelsey-Hayes Company, Romulus, Mich.

[22] Filed: Sept. 22, 1969 [21] Appl. No.: 859,777

FOREIGN PATENTS OR APPLICATIONS 722,521 11/1965 Canada ..60/54.6 P

7 Primary Examiner--Edgar W. Geoghegan 521 115.1:1 ..611/516 11, 60/546 1 Assist! Examiner-A- Zupcic 511 mm ..1 115111 7/1111 Attorney-Harness, Dickey & Pierce [58] lFlzeldl 111 Search ..251/38, 44; 60/545 F, 54.6 P

[57] AfiSTlRACT [56] Remmmm Gated A power booster for a brake system in which input force and UNITED STATES PATENTS input displacement hysteresis relative to output pressure is avoided or minimized.

1,651,689 12/1927 Freeze ..251/44 2,689,706 9/ 1954 Carlson ..25 1/38 1 11 (111111111115, 11 Drawing lFigm-e s has lll llllE Gll lATlihi G HXHMAJULWC SUIVHVIARY BACKGROUND i Til-TE ll li/iENTlUhl The present invention relates to power boosters for brake systems.

in conventional power boosters output pressure is normally a function of displacement of a pilot valve and input force resulting from pressure feedback. Because of friction in the system the relationship between displacement and input force and output pressure will be different for increasing displacement and force and decreasing displacement and force. This difference can be considered as hysteresis. it is desirable to avoid such hysteresis and in the present invention this is done in a booster using hydraulic power by incorporating time integration in the pilot valve motion.

Therefore it is an object of the present invention to provide a novel brake booster utilizing time integration in the pilot valve motion whereby hysteresis of input displacement and input force with output pressure is eliminated or minimized.

it is another object to provide a novel bralce booster which provides for manual operation of the bralres in the event of a power failure.

it is another general ob ect of the present invention to pro vide a novel brake booster.

Other objects, features, and advantages of the present invention will become apparent from the subsequent description and the appended claims talten in conjunction with the accompanying drawing.

The FlG. is a partial schematic drawing with some parts shown in section of apparatus embodying features of the present invention.

Looking now to the drawing, a booster lid is shown to be connected to front and rear brake systems llill and lid via fluid lines in and if respectively. Booster lid is energized from a source of hydraulic pressure Ell having a pressurized outlet 22 and a return 2d. The booster lid is actuated via a foot pedal 2b which has a foot application leg portion filtl connected to a booster application leg portion E li to define an inverted V pivotally supported at its apex The booster ill includes a valve housing lid which has a central cavity defining a plurality of coartially extending chambers Ed, 3d, all and 42;. A. pressure feedback piston dd is slidably supported in chamber as. The piston dd has a head portion to which carried an annular seal db which provides a seal with the wall of chamber 3h). Stem portions fill and 1'52 extend inwardly and outwardly, respectively, from head portion At coil spring assembly 5dengages the head portion do and normally urges the piston outwardly from chamber 3b with stem portion all being urged into engagement with input leaf spring do which is secured to the booster appiication leg portion Lilli of foot pedal as causing pedal lid to be pivoted to its deactuated position-engaging pedal stop An annular seal or is supported at the extreme inner end of inner stem portion fill. The chamber 3 h is in direct communication, via passage till, with a booster chamber oil which houses a booster piston rid for sliding action. An annular seal (r7 seals opposite sides of piston W ll in chamber as; the booster piston actuates a master cylinder assembly or, which can be a dual master cylinder generally of a conventional construction. lFluid lines to and 1th are connected to master cylinder assembly tilt whereby the braltes for the front and rear wheels can be actu ated. A mechanical override plunger lid is slidably supported in piston dd and housing and is appropriately sealed by seals 7ft and "72. The plunger dd acts on an actuating piston "id in master cylinder assembly at and booster piston dd acts on master cylinder piston through snapring 7b secured to plunger on. A light spring til normally holds booster piston as against the ring lb. Thus fluid pressure in chamber also appears in booster chamber till and acts on booster piston A control valve hill is sliclably supported, via a f iange portion flit, in the chambers Bill and dil which are of the same diameter which is larger than that of chamber fit seal in portion flit. separates the chambers Eltl and dill.

The control valve bill, which functions as a throttle valve, has a forward portion dd which extends into chamber Sill and has a seal which sealingly engages the shoulder t ll of chamber to normally seal chamber 38 from chamber as. The control valve dd has a rearward portion 92 which extends through chamber dil and into chamber M. A ring M separates chambers ill and ift and is held against the forward shoulder of chamber d2 by a spring 9b: which acts against a cap 98 and retaining ring llt'lll located at the rearward end of chamber 42. The cap Wit and ring 9 are sealed at their outer extremities via seals llllI-l and lltld, respectively. The rearward portion 92 extends through ring 9d and is sealed therewith via a seal the. A bleed port will, through the flange portion 8?; communicates chambers 3th and ill. A pilot port lllltll extends through rearward portion @12- to communicate chambers db and M. This port illltl is normally closed by a pilot valve ll T2.

The control valve lid, which also functions as a throttle valve, has a through bore lllld which terminates at its forward end in a counterbore portion llllb. The pilot valve lllfi is sliclably supported in bore lllld and has a head portion lllltl in counterbore portion llllb and a rod portion ll2ll in the smaller diameter portion of bore lllld. Seals T22 and T23 seal head portion llllli and rod portion ll2ll, respectively. A valve seal ring 11% is fired to the outer end of rod portion ll2ll and has a seal lilo which can overengage the rearward end of pilot port llltll to close that port. The pilot valve Illlfl has a through bore ll ll which can communicate chambers as and dill. The seal to on feedback piston can engage the forward end of head portion ills of piiot valve liilil to block the forward end of bore rss. A. passage 132 through the forward portion fits of control valve d ll communicates counterbore lllo and chamber The pressure outlet line 22 from source 2% is connected to chamber fill via port 113d while return line 24 is connected to chamber d2 via port T36. Prior to brake application chambers db and db and counterbore llllo will be at the high pressure from line 22 and chambers 36 and 42 and booster chamber s2 will be at the low pressure of return line 2d; hence the master cylinder assembly so will not be actuated. Thus, prior to brake application, the pressure feedback piston dd, control valve lid, and pilot valve lllill are in the positions shown, which are established and held by differential pressure acting on differential piston areas in the case of the pilot valve lllfl and control valve hill and by the light spring M in the case of the pressure feedback piston di l. When the pedal 1% is depressed the pressure feedback piston M is moved until the seal to en gages head portion lift and bore lild is closed. As the pedal is further depressed the pilot valve M2 is pushed to the right by the pressure feedback piston dd opening the pilot port llllll and reducing the pressure in the control valve chamber dd. The pressure on chamber dill will be reduced at a rate determined by the differential flow rate between the input through the pilot chamber bleed port lllld and the outflow through the pilot port lllltll. The rate of outflow from pilot port llllll will be controlled by the position of valve seal 11% which functions as a throttle valve. The control valve bid will move to the right at a speed equal to the differential volume flow divided by the effective control valve piston area. As soon as the lap at the shoulder hill is traversed, fluid will enter the pressure feedback chamber 36 and will flow to the booster chamber as displacing the booster piston st and applying the brake. As fluid pressure builds up in master cylinder assembly so the reaction force will retard the motion of the booster piston n41 causing pressure to increase in the booster cylinder 62 and in the pressure feedback chamber Elli. This pressure causes a reaction to be transmitted to the bralte pedal through spring 5b. The reaction force on the pressure feedback piston dd simultaneously causes it to move to the left as spring so is compressed. This causes the pilot valve llllh to move to the left towards a position closing the pilot valve port lllld. its flow through port llllill is throttled, by valve seal T26, pressure increases in the chamber dd causing the control valve till to move to the left at a rate proportional to the flow differential between the bleed 3 port 108 and the pilot port 110, closing the control valve 80 (against shoulder 90) and holding booster pressure and hence booster effort at a level proportional to pedal effort.

When pedal effort is released the pressure feedback piston 44 moves to the left, opening the bore 130 and allowing booster pressure to decrease until equilibrium is again reached with pedal effort.

in the event of hydraulic power failure of supply 20, the pilot valve 112 and control valve 80 are free to move to the right so that the pedal 26 may be depressed far enough to permit direct application of the brakes through the mechanical override plunger 68.

With the valve assembly 10, as noted, hysteresis and/or lag between input force and displacement and output pressure is minimized. This can be seen from the following analysis in which the following terms apply:

P pressure to brakes from master cylinder assembly 64 P rate of change of pressure P Xv rate of change of Xv Xv displacement of control valve 80 Xc displacement ot'pilot valve 112 Fi input force at pedal 26 Xi input displacement ofpcdal 26 k spring rate ofspring 56 K1, K2, K3 various constants si HP) (Laplace transform) S2 f (P) (Laplace transform) The control valve 80 acts as a throttle valve such that the rate of flow into chamber 36 from chamber 38 will be a function of the displacement of the valve 80 away from shoulder 90; thus the rate of change of pressure at booster cylinder 62 and hence at master cylinder assembly 66 is proportional to the displacement of control valve 80 whereby: (l P=K 1X v.

Note that the rate of displacement of the control valve 80 is controlled by the differential flow rate from chambers 38 to 40 to 42. This will be controlled by valve 126 which also acts as a throttle valve whereby flow out from port 110 will be at a rate determined by the displacement of pilot valve 112 relative to control valve 80; Thus the rate of displacement of the control valve 80 is proportional to the difference in displacement between the control valve 80 and pilot valve 112, whereby: (2) Xv=K2(XcXv).

Thus, control valve 80 will move to the right at a speed equal to the differential volume flow divided by the effective control valve piston area. Equation (2) provides the required integration, whereby: (3) X v=K2(Xc-X v)dt The output pressure is also proportional to the input force and input dispiacement of the pedal 26 as acting through spring 56. Thus:

(4) Fi=K3P, and (5) Fi=k(Xi-Xc) Using Laplace transform notation equations (1), (2), (4) and (5) can be solved for Xi, whereby:

From an examination of equation 6 it can be seen that the apparatus of FIG. 1 will provide output pressure which is a time integral function of input displacement Xi and, of course,

of Xv. Considering the operation of the structure of the drawing, it can be seen that the motion of the various valves in any one direction will be slight whereby frictional effects will be almost negligible. With such a structure hysteresis effects will therefore be minimized.

While it will be apparent that the preferred embodiment of the invention disclosed is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the invention.

What is claimed is:

1. A hydraulic brake booster valve actuable by a vehicle operator through a pedal member comprising: control valve means actuable to provide fluid braking pressure at a rate varying in accordance with variations in the magnitude of the displacement of said control valve means, pilot valve means actuable to vary the rate of displacement of said control valve means as a function of the magnitude of the displacement of said pilot valve means, actuating means connected to the pedal member and said pilot valve means for displacing said pilot valve means in response to actuation of the pedal member, said actuating means including a pressure feedback means for providing a force varying in magnitude in accordance with variations in magnitude of the braking pressure and resilient means for transmitting the feedback force from said feedback means to the pedal member.

2. The brake booster valve of claim l with said pilot valve means actuable to vary the rate if displacement of said control valve means as a function of the relative displacement of said pilot valve means relative to said control valve means.

3. The brake booster valve of claim 2 operable with a source of fluid pressure with said control valve means being displaced by fluid from the source and with the rate of displacement of said control valve means varying in accordance with the rate of fluid flow from the source acting on said control valve means, said pilot valve means comprising a first pilot throttle valve movable to vary the rate of fluid flow acting on said control valve means in accordance with the relative displacement of said pilot throttle valve.

4. The brake booster valve of claim 3 with said control valve means comprising a control throttle valve movable to vary the rate of flow of fluid for braking pressure from the source in accordance with the displacement of said control throttle valve.

5. The brake booster valve of claim 4 further comprising a housing having a plurality of fluid chambers, said control valve means comprising a control valve body carrying said control throttle valve with said control valve body being slidably supported in one of said chambers, said control valve body including a bleed port communicating said one of said chambers on opposite sides of said control valve body, means communicating one side of said one of said chambers to the high-pressure side of the source, said control valve body including a pilot port communicating the other side of said one of said chambers with a second chamber connected to the return side of the source, said pilot valve means comprising a pilot valve body mounted with said control valve body for relative movement therewith, said pilot valve body carrying said pilot throttle valve located in said second chamber for cooperation with said pilot port for controllably varying the fluid flow therethrough, a feedback chamber communicable with said one of said chambers with the fluid flow to said feedback chamber being controlled by said control throttle valve, said pressure feedback means comprising a feedback piston slidably supported in said feedback chamber and actuable for providing the feedback force, said pilot valve body havingv a passage normally communicating said feedback chamber and said second chamber, said feedback piston being movable to engage said pilot valve body and to block said passage and to displace said pilot valve body to open said pilot throttle valve, said control valve body being movable to open said control throttle valve at a rate which is a function of the flow rate of fluid through said bleed port and said pilot port as affected by the displacement of said pilot throttle valve, and booster piston means actuable in response to the magnitude of fluid pressure in said feedback chamber for applying the brakes at a pressure determined by said magnitude of fluid pressure.

6. The brake booster valve of claim 5 with said resilient means comprising a spring member connected between the pedal member and said feedback piston.

7. The brake booster of claim 5 for actuation of a master cylinder, said booster means comprising a booster piston assembly operable on the master cylinder in response to the magnitude of fluid pressure in said feedback chamber, said piston assembly including a rod member engageable by the brake pedal in the event of failure of the source of fluid pressure whereby the master cylinder can be directly actuated by the vehicle operator through the brake pedal; said feedback piston, said pilot valve body and said control valve body normally being positioned to prevent engagement of said rod member and the brake pedal and being displaced in response to failure of the source to permit such engagement.

8. The brake booster valve of claim ll further comprising auxiliary means actuable by the pedal to provide pressurized brake pressure, said pilot valve means and control valve means being operable from a source of fluid pressure to nor mally provide the operative connection between said actuating means and the pedal member which normally maintains the pedal out of actuating position for said auxiliary means; said pilot valve means and control valve means being moveable upon a loss of pressure from the source to permit actuation of said auxiliary means by the brake pedal.

94 A hydraulic brake booster valve operable from a source of fluid pressure having a highand a low-pressure side and actuable by a vehicle operator through a pedal member comprising: control valve means actuable to provide fluid braking pressure from the source at a rate varying in accordance with variations in the magnitude of the displacement of said control valve means, pilot valve means actuable to vary the rate of displacement of said control valve means as a function of the magnitude of the displacement of said pilot valve means, actuating means connected to the pedal member and said pilot valve means for displacing said pilot valve means in response to actuation of the pedal member, said pilot valve means con nected to the high-pressure side of the source and normally urged by fluid from the high-pressure side towards a condition of no displacement relative to said control valve means.

it). A hydraulic brake booster valve operable from a source of fluid pressure having a high and a low-pressure side and actuable by a vehicle operator through a pedal member comprising: control valve means actuable to provide fluid braking pressure from the source at a rate varying in accordance with variations in the magnitude of the displacement of said control valve means, pilot valve means actuable to vary the rate if displacement of said control valve means as a function of the magnitude of the displacement of said pilot valve means, actuating means connected to the pedal member and said pilot valve means for displacing said pilot valve means in response to actuation of the pedal member, said pilot valve means connected to the high-pressure side of the source and normally urged by fluid from the high-pressure side towards a condition of no displacement relative to said control valve means, said control valve means being displaced by fluid from the source and with the rate of displacement of said control valve means varying in accordance with the rate of fluid flow from the source acting on said control valve means, said pilot valve means comprising a first pilot throttle valve movable to vary the rate of fluid flow acting on said control valve means in accordance with the relative displacement of said pilot throttle valve, fluid conduit means connecting said first pilot throttle valve to the high-pressure side of the source for normally urg ing said first throttle valve towards a condition of no relative displacement.

Patent No. 9 436 Deitefi February 22 1972 Inventofls) g iorol It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 23 "123" should he 124 column 3 line 21 "P" should be mm P (first occurrence); column 3 line 22 "Xv" (first occum'elrtme) shoulfl be Xy column 3 line 28 "(PV should be (E PQ column 3 line 29 "(P)" ShOllld b8 W cglumn 4, line 18 "if" should be we of eolumn 6 line 9 "if" should he W of o Signed and sealed this 19th day of September 1972.

(SEAL) I Attestf EDWARD M .FLETCHER,JR, ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM po-mso (10-69) UlECOMM-DC 00370-P69 0,5 GOVERNMENT PRINTING OIVICI I". 0-8604 

1. A hydraulic brake booster valve actuable by a vehicle operator through a pedal member comprising: control valve means actuable to provide fluid braking pressure at a rate varying in accordance with variations in the magnitude of the displacement of said control valve means, pilot valve means actuable to vary the rate of displacement of said control valve means as a function of the magnitude of the displacement of said pilot valve means, actuating means connected to the pedal member and said pilot valve means for displacing said pilot valve means in response to actuation of the pedal member, said actuating means including a pressure feedback means for providing a force varying in magnitude in accordance with variations in magnitude of the braking pressure and resilient means for transmitting the feedback force from said feedback means to the pedal member.
 2. The brake booster valve of claim 1 with said pilot valve means actuable to vary the rate if displacement of said control valve means as a function of the relative displacement of said pilot valve means relative to said control valve means.
 3. The brake booster valve of claim 2 operable with a source of fluid pressure with said control valve means being displaced by fluid from the source and with the rate of displacement of said control valve means varying in accordance with the rate of fluid flow from the source acting on said control valve means, said pilot valve means comprising a first pilot throttle valve movable to vary the rate of fluid flow acting on said control valve means in accordance with the relative displacement of said pilot throttle valve.
 4. The brake booster valve of claim 3 with said control valve means comprising a control throttle valve movable to vary the rate of flow of fluid for braking pressure from the source in accordance with the displacement of said control throttle valve.
 5. The brake booster valve of claim 4 further comprising a housing having a plurality of fluid chambers, said control valve means comprising a control valve body carrying said control throttle valve with said control valve body being slidably supported in one of said chambers, said control valve body including a bleed port communicating said one of said chambers on opposite sides of said control valve body, means communicating one side of said one of said chambers to the high-pressure side of the source, said control valve body including a pilot port communicating the other side of said one of said chambers with a second chamber connected to the return side of the source, said pilot valve means comprising a pilot valve body mounted with said control valve body for relative movement therewith, said pilot valve body carrying said pilot throttle valve located in said second chamber for cooperation with said pilot port for controllably varying the fluid flow therethrough, a feedback chamber communicable with said one of said chambers with the fluid flow to said feedback chamber being controlled by said control throttle valve, said pressure feedback Means comprising a feedback piston slidably supported in said feedback chamber and actuable for providing the feedback force, said pilot valve body having a passage normally communicating said feedback chamber and said second chamber, said feedback piston being movable to engage said pilot valve body and to block said passage and to displace said pilot valve body to open said pilot throttle valve, said control valve body being movable to open said control throttle valve at a rate which is a function of the flow rate of fluid through said bleed port and said pilot port as affected by the displacement of said pilot throttle valve, and booster piston means actuable in response to the magnitude of fluid pressure in said feedback chamber for applying the brakes at a pressure determined by said magnitude of fluid pressure.
 6. The brake booster valve of claim 5 with said resilient means comprising a spring member connected between the pedal member and said feedback piston.
 7. The brake booster of claim 5 for actuation of a master cylinder, said booster means comprising a booster piston assembly operable on the master cylinder in response to the magnitude of fluid pressure in said feedback chamber, said piston assembly including a rod member engageable by the brake pedal in the event of failure of the source of fluid pressure whereby the master cylinder can be directly actuated by the vehicle operator through the brake pedal; said feedback piston, said pilot valve body and said control valve body normally being positioned to prevent engagement of said rod member and the brake pedal and being displaced in response to failure of the source to permit such engagement.
 8. The brake booster valve of claim 1 further comprising auxiliary means actuable by the pedal to provide pressurized brake pressure, said pilot valve means and control valve means being operable from a source of fluid pressure to normally provide the operative connection between said actuating means and the pedal member which normally maintains the pedal out of actuating position for said auxiliary means; said pilot valve means and control valve means being moveable upon a loss of pressure from the source to permit actuation of said auxiliary means by the brake pedal.
 9. A hydraulic brake booster valve operable from a source of fluid pressure having a high- and a low-pressure side and actuable by a vehicle operator through a pedal member comprising: control valve means actuable to provide fluid braking pressure from the source at a rate varying in accordance with variations in the magnitude of the displacement of said control valve means, pilot valve means actuable to vary the rate of displacement of said control valve means as a function of the magnitude of the displacement of said pilot valve means, actuating means connected to the pedal member and said pilot valve means for displacing said pilot valve means in response to actuation of the pedal member, said pilot valve means connected to the high-pressure side of the source and normally urged by fluid from the high-pressure side towards a condition of no displacement relative to said control valve means.
 10. A hydraulic brake booster valve operable from a source of fluid pressure having a high and a low-pressure side and actuable by a vehicle operator through a pedal member comprising: control valve means actuable to provide fluid braking pressure from the source at a rate varying in accordance with variations in the magnitude of the displacement of said control valve means, pilot valve means actuable to vary the rate if displacement of said control valve means as a function of the magnitude of the displacement of said pilot valve means, actuating means connected to the pedal member and said pilot valve means for displacing said pilot valve means in response to actuation of the pedal member, said pilot valve means connected to the high-pressure side of the source and normally urged by fluid from the high-pressure side towards a condition of no displacement relaTive to said control valve means, said control valve means being displaced by fluid from the source and with the rate of displacement of said control valve means varying in accordance with the rate of fluid flow from the source acting on said control valve means, said pilot valve means comprising a first pilot throttle valve movable to vary the rate of fluid flow acting on said control valve means in accordance with the relative displacement of said pilot throttle valve, fluid conduit means connecting said first pilot throttle valve to the high-pressure side of the source for normally urging said first throttle valve towards a condition of no relative displacement. 